Page 172 - ICSE Math 7

2. If AB || CD, find x for each of the following figures.

P C A C
55° A
A B 40° E x 2x F
(a) (b) E x F (c)

C x D D B
Q B D

E x F

45°
3. If AB, CD and EF are parallel to each other. Find the values of y
x, y and z. C D
z 40°
A B
4. If l || m, find the values of the unknown angles.

x y y
l x m
68°
(a) 125° (b) 62° y x (c)
m 58° 60°
110° m l
l

m l
m 2x + 50°
y y z l
(d) z (e) (f) x + 100°
x x x m
30° l 55° y

AT A GLANCE

¾ A point is a mark of position. It has no length, breadth and thickness.
¾ A line is a collection of points along an endless straight path.
¾ A line segment is a part of a line from one fixed point to the other.
¾ A ray is a part of a line which starts from a fixed point and moves endlessly in the same direction.
¾ A plane is a flat surface having infinite length and breadth.
¾ Two lines lying in the same plane which do not meet even when extended indefinitely are known
as parallel lines.
¾ Two lines lying in the same plane and having a common point are known as intersecting lines.
¾ Two intersecting lines making an angle of 90° at the point of intersection are known as
perpendicular lines.

¾ Three or more points are known as collinear if all of them lie on the same line.
¾ Three or more lines are known as concurrent if all of them pass through the same point.
¾ Two rays having the same initial point form an angle.
¾ Two angles are called complementary angles if the sum of their magnitudes is equal to 90° and
are called supplementary angles if the sum of their magnitudes is equal to 180°.

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